Spectral signs of the internal heavy-atom effect in aliphatic carbonyl compounds

The CNDO/S method has been applied to the internal effect of Si on the electronic spectrum of the acetone molecule; there is a considerable bathochromic shift and an increase in the \(S_0 \to S_{n\pi ^ * } \) intensity for theα-silyl ketones, while theβ-silyl ketons give only an increase in the intensity of \(S_0 \to S_{n\pi ^ * } \) absorption relative to acetone. The heavy atom substantially alters \(f_{S_0 \to T_{n\sigma ^* } } \) and \(\tau _{T_{n\sigma ^* } }^0 \) but has little effect on \(f_{S_0 \to T_{n\pi ^* } } \) and \(\tau _{T_{n\pi ^* } }^0 \) .     

Alpha decay of neutron-deficient rhenium and osmium isotopes

Neutron-deficient osmium and rhenium isotopes were produced by bombarding an enriched¹⁴⁴Sm target with beams of²⁷Al and²⁸Si. Previously reported decay data concerning^168,169,170Os were confirmed. Three newα groups, observed in the¹⁴⁴Sm+²⁷Al reaction, were assigned to the decay of^166,167,168Re based on excitation functions,α-energy systematics and theoretical half-life predictions. Their decay properties are: $$\begin{gathered} {}^{166}\operatorname{Re} , E_\alpha = 5,372 (10) keV, T_{1/2} = 2.8 (3) s; \hfill \\ {}^{167}\operatorname{Re} , E_\alpha = 5,136 (8) keV, T_{1/2} = 6.1 (2) s and \hfill \\ {}^{168}\operatorname{Re} , E_\alpha = 4,894 (10) keV, T_{1/2} = 6.9 (8) s. \hfill \\ \end{gathered}$$ It is proposed that twoα groups, observed in the¹⁴⁴Sm+²⁸Si reaction, originate from isomeric states in^168,169Re. Our measured data for the isomeric states are: $$\begin{gathered} {}^{168m}\operatorname{Re} , E_\alpha = 5,250 (10) keV, T_{1/2} = 6.6 (15) s and \hfill \\ {}^{169m}\operatorname{Re} , E_\alpha = 5,050 (10) keV, T_{1/2} = 12.9 (11) s. \hfill \\ \end{gathered} $$      

Scattering of a few-cycle laser pulse by a single relativistic electron

The scattering of a single relativistic electron with few-cycle plane wave laser pulse with intensity of about $I=1.38\times 10^{14}\,\text{ W/cm }^{2}$ is theoretically and numerically analyzed in the linear regime, and the radiated energy spectra of electron shows that zeptosecond X-ray pulses can be supported. The influences of the initial carrier-envelope phase offset $\varphi _0$ of the incident few-cycle laser pulses are studied, and the results demonstrate that a single zeptosecond pulse can be produced from scattering by using a single-cycle laser pulse with fixed initial carrier-envelope phase offset $\varphi _0 =\pi /2$ . It is discovered that the influence of the initial carrier-envelope phase $\varphi _0$ on the spectrum of the radiation is apparent for low and high frequency of the spectrum, but there is no influence of the central part of the spectrum.     

Electromagnetic moment investigation of two short-lived isomeric states in118Sb

Two short-lived isomeric states in¹¹⁸Sb have been investigated by the¹¹⁸Sn(p, n),¹¹⁸Sn(d, 2n) and¹¹⁵In(α, n) reactions. The TDPAD method on solid and liquid metallic targets was used to measure the electromagnetic moments of these states. The results of the experiments are: $$\begin{gathered} T_{1/2} = 13.4{\text{ }}(3){\text{ }}ns I^\pi = 3^ - {\text{ }}g = - 1.254(31){\text{ }}|Q| = 0.25{\text{ }}(5){\text{ }}b, \hfill \\ T_{1/2} = 22.8{\text{ }}(4){\text{ }}ns I^\pi = 7^ + {\text{ }}g = + 0.680(18){\text{ }}|Q| > 1.4{\text{ }}b. \hfill \\ \end{gathered}$$ Pure \([\pi 2d_{5/2} \otimes v1h_{1{\text{ }}1/2} ]_{3 - }\) and \([\pi 1g_{9/2}^{ - 1} \otimes v2d_{5/2}^{ - 1} ]_{7 + }\) configurations have been established for the two isomeric states. An experimental evidence concerning the participation of the 1g ₉ ^2/?1 proton shell-model intruder excitation into the positive parity low-lying level structure of the odd-odd¹¹⁸Sb nucleus was obtained.     

Inter- and Intramolecular Relaxation in Molecular Liquids by Field Cycling 1H NMR Relaxometry

Field cycling ¹H nuclear magnetic resonance (NMR) relaxometry is applied to study rotational as well as translational dynamics in molecular liquids. The measured relaxation rates, $ T_{1}^{ - 1} \left( \omega \right) \equiv R_{1} \left( \omega \right) $ , contain intra- and intermolecular contributions, $ R_{{1,{\text{intra}}}}^{{}} \left( \omega \right) $ and $ R_{{ 1 , {\text{inter}}}}^{{}} \left( \omega \right) $ . The intramolecular part is mediated by rotational dynamics, the intermolecular part by translation as well as rotation. The rotational impact on the intermolecular relaxation (eccentricity effect) is due to the spins not located in the molecule’s center. The overall relaxation rate is decomposed into $ R_{{1,{\text{intra}}}}^{{}} \left( \omega \right) $ and $ R_{{ 1 , {\text{inter}}}}^{{}} \left( \omega \right) $ by isotope dilution experiments. It is shown that the eccentricity model (Ayant et al. in J. Phys. (Paris) 38:325, 1977) reproduces fairly well the bimodal shape of $ R_{{ 1 , {\text{inter}}}}^{{}} \left( \omega \right) $ for o-terphenyl and glycerol. As the relaxation contribution associated with translational dynamics dominates at lower frequencies, the overall relaxation rate shows a universal linear behavior when plotted versus square root of frequency. This allows determining the self-diffusion coefficient, D, in a model-independent way. It is demonstrated that the shape of NMR master curves comprising relaxation data for different temperatures, linked by frequency–temperature superposition, reflects the relative strength of translational and rotational contributions.     

H ̄ + production from collisions between positronium and keV antiprotons for GBAR

In the framework of the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment, cross sections for antihydrogen ion ( \(\bar {\mathrm {H}}^{+}\) ) production in collisions between antiprotons ( \(\bar {\mathrm {p}}\) ) and excited positronium atoms (Ps), with intermediate production of antihydrogen ( \(\bar {\mathrm {H}}\) ), have been computed using a perturbative theory, namely Continuum Distorted Wave - Final State (CDW-FS). The results suggest to use antiprotons at 1, 2 or 6 keV with, respectively, Ps(3p,3d), Ps(2p) or no Ps excitation. A simulation using these cross sections is under development to investigate the reaction chamber geometry and the parameters of the different beams (positrons, antiprotons and laser). This simulation, focusing on Ps(3d), predicts at least one \(\bar {\mathrm {H}}^{+}\) ion per pulse of 3·10⁶ \(\bar {\mathrm {p}}\) at 1 and 6 keV, and highlights both the interest of positronium excitation and the need for short pulses of particles.     

Characteristics of π−,\bar p,and antinuclei frompp collisions

An investigation of inclusivepp→π^?+? in terms of the covariant Boltzmann factor (BF) including the chemical potential μ indicates a) that the temperatureT increases less rapidly than expected from Stefan's law, b) that a scaling property holds for the fibreball velocity of π^? secondaries, leading to a multiplicity law like ～E _cm ^1/2 at high energy, and c) that μ_π is related to the quark mass: μ_π=2m _q ?m _π the quark massm _q determined by \(T_{\pi ^ - } \) at \(\bar pp\) threshold beingm _q =3T_π?330 MeV. Because ofthreshold effects \(T_{\bar p}< T_{\pi ^ - } \) , whereas \({{\mu _p } \mathord{\left/ {\vphantom {{\mu _p } {\mu _{\pi ^ - } }}} \right. \kern-0em} {\mu _{\pi ^ - } }} \simeq {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-0em} 2}\) as expected from the quark contents of \(\bar p\) and π. The antinuclei \(\bar d\) and \({{\bar t} \mathord{\left/ {\vphantom {{\bar t} {\overline {He^3 } }}} \right. \kern-0em} {\overline {He^3 } }}\) observed inpp events are formed by coalescence of \(\bar p\) and \(\bar n\) produced in thepp collision. Semi-empirical formulae are proposed to estimate multiplicities of π^?, \(\bar p\) and antinuclei.     

Zero value of the Schwarzschildian mass of asymptotically euclidian time-symmetrical gravitational waves

It is shown that a coordinate system with simple coordinate conditions can be chosen such that one can explicitly see that the Schwarzschildian mass of an asymptotically Euclidian time-symmetrical system of gravitational waves is equal to zero. It is explicitly seen in the coordinate system with coordinate conditions ? _i (?gg ^ik)=0 and in the set of coordinate systems with the coordinate condition ? _i (?gg ⁰ⁱ )=0. In this set of coordinate systems one of the field equations can be written in the form \( - 8\pi \surd ( - g)(T_0^0 - \tfrac{1}{2}T) = \partial _\alpha L_0^{0\alpha } \) where \(L_i^{kn} = \tfrac{1}{2}\surd ( - g)(g^{mn} \Gamma _{im}^k - g^{km} \Gamma _{im}^k )\) , α=1, 2, 3. From this equation it follows that \(m = 2\smallint ({\rm T}_0^0 - \tfrac{1}{2}T)\surd ( - g) dV\) , andm=0 atT _i ^k =0.     

Half-life measurements in59Co,141Pr and227Ac

The half-lives of the 1291.6 keV level in⁵⁹Co, 145.43 keV level in¹⁴¹Pr and 27.35 keV level in²²⁷Ac have been measured using leading edge and zero-crossover timing techniques. The decay curves analysed by moments, Laplace transform and slope methods gave the following half-life values: $$\begin{gathered} T_{\tfrac{1}{2}} (1291.6 keV level in {}^{59}Co) = (0.538 \pm 0.004) ns \hfill \\ T_{\tfrac{1}{2}} (145.43 keV level in {}^{141}\Pr ) = (1.82 \pm 0.04) ns \hfill \\ T_{\tfrac{1}{2}} (27.35 keV level in {}^{227}Ac) = (41.0 \pm 1.1) ns. \hfill \\ \end{gathered} $$ From the measured half-lives, the reduced transition probabilitiesB(M1)↓,B(E2)↓ for gamma transitions de-exciting the above mentioned levels in⁵⁹Co and¹⁴¹Pr are determined and compared with single particle, intermediate coupling and Sorensen estimates. In²²⁷Ac, absolute transition probability for the 27.35 keV transition is determined and compared with single particle and Nilsson estimates.     

Identification of 180Pb

The α decay of the new isotope ¹⁸⁰Pb was observed in ⁴⁰Ca bombardments of ¹⁴⁴Sm: E _α = 7.23(4) MeV, and, \({T_{1/2}} = \left( {4_{ - 2}^{ + 4}} \right){\text{ ms}}\) . With this decay energy and the known mass of ¹⁷⁶Hg, the mass excess of ¹⁸⁰Pb was calculated to be ?1.98(5) MeV.     

Phase sensitivity of light dynamics in PT-symmetric couplers

We study the sensitivity of light dynamics to the internal phase of propagating pulses in the two types of $\mathcal {PT}$ -symmetric models. The first is a waveguide array with an embedded pair of waveguides with gain and loss, called $\mathcal {PT}$ -coupler, and the second is a planar coupler which models a chain of $\mathcal {PT}$ -symmetric couplers. For the first model we investigate the soliton scattering on the mode localized on the coupler, while for second model we study the collision of two breathers. For both models we find that the light dynamics is sensitive to the internal phases of the interacting pulses. Particularly, the $\mathcal {PT}$ -symmetry breaking can take place or not, depending on the internal phases of two signals having identical other parameters.     

Ultrafast optical responses of three-level systems in β-carotene: Resonance to a high-lying n 1 A g − excited state

Ultrafast optical phenomena in all-trans-β-carotene have been investigated by femtosecond absorption and fluorescence spectroscopy. Following a resonant pump pulse, both fluorescence and absorbance changes have a decay time of 150 fs. The signals are assigned to the lowest optically allowed singlet excited state, 1¹ B _u ⁺ . Transmittance changes induced by nonresonant pump pulses depend on the pump photon energy. They are interpreted in terms of the ac Stark effect in three-level systems and two-photon absorption of the pump and probe pulses generating a high-lying n ¹ A _g ^? state.     

Optical detected ESR in the4 S 3/2 excited state of Er:YCl3

The electron spin resonance in the⁴ S _3/2 excited state of Er³⁺ in yttrium trichloride was studied by optical detection techniques. From angular dependence of the resonance field the principle value of theg-tensor in direction of the twofold crystal axis was deduced to beg∥=3.350±0.004 and the perpendicular valueg⊥ in the crystallographica-b-plane was extrapolated to beg⊥=2.857±0.004. The lifetime of the excited state is found to be temperature independent with τ _r =(1.62±0.02)·10^?3 sec and the spin lattice relaxation timeT ₁ was determined in the temperature region 1.5 to 2.1 °K by observing the recovery of the fluorescent light signal after a microwave saturation pulse was switched off.T ₁ is found to follow a direct process with \(T_1^{ - 1} = k \cdot cth\left( {\frac{{\rlap{--} h\omega }}{{2kT}}} \right)\) .     

A windowless hydrogen gas target for the measurement of 7Be(p, $ \gamma$ )8B with the recoil separator ERNA

Using the Coulomb and proximity potential model (CPPM) we have investigated the cluster decays of the isotopes ^212-240Pa, ^219-245Np, ^228-246Pu, ^230-249Am and ^232-252Cm leading to doubly magic ²⁰⁸Pb and its neighboring nuclei, which are not experimentally detected but which may be detectable in the future. It is found that most of the decays are favourable for experimental measurements (i.e., $T_{1/2}<10^{30}$ s) and this observation will serve as a guide to future experiments. Our study reveals the role of doubly magic ²⁰⁸Pb daughter nuclei and near doubly magic nuclei in the cluster decay process. In order to make a comparison with CPPM we also calculated the logarithmic half-lives using the Universal formula for the cluster decay (UNIV) by Poenaru et al., the Universal Decay Law (UDL) and the Scaling Law of Horoi et al., and they are found to be in good agreement. The Geiger-Nuttall plots of $log_{10}(T_{1/2})$ versus $Q^{-1/2}$ for various clusters from different isotopes of heavy parent nuclei have been studied and are found to be linear.     

A High-Field EPR Study of the Accelerated Dynamics of the Amorphous Fraction of Semicrystalline Poly(dimethylsiloxane) at the Melting Point

The reorientation of a small paramagnetic tracer in poly(dimethylsiloxane) (PDMS) has been investigated by high-field electron paramagnetic resonance spectroscopy at a Larmor frequency of 285 GHz. The tracer is confined in the disordered phase of the semicrystalline PDMS. A sudden change of the rotational dynamics is observed close to the melting point (213 K) of the crystallites. This points to strong coupling between the crystalline and the disordered fractions of PDMS. Below the glass transition ( \(T_\mathrm{g} \sim 150 \mathrm{K}\) ), the tracer reorientation occurs via small angle jumps, with no apparent distribution of the correlation times. Above \(T_\mathrm{g}\) , a power-law distribution of correlation times is evidenced.     

Radiative and semileptonic B decays involving higher K-resonances in the final states

We study the radiative and semileptonic B decays involving a spin-J resonant $K_{J}^{(*)}$ with parity (?1) ^J for $K_{J}^{*}$ and (?1) ^J+1 for K _J in the final state. Using large energy effective theory (LEET) techniques, we formulate $B\to K_{J}^{(*)}$ transition form factors in the large recoil region in terms of two independent LEET functions $\zeta_{\perp}^{K_{J}^{(*)}}$ and $\zeta_{\parallel}^{K_{J}^{(*)}}$ , the values of which at zero momentum transfer are estimated in the BSW model. According to the QCD counting rules, $\zeta_{\perp,\parallel}^{K_{J}^{(*)}}$ exhibit a dipole dependence in q ². We predict the decay rates for $B\to K_{J}^{(*)}\gamma$ , $B\to K_{J}^{(*)}\ell^{+}\ell^{-}$ and $B\to K_{J}^{(*)}\nu \bar{\nu}$ . The branching fractions for these decays with higher K-resonances in the final state are suppressed due to the smaller phase spaces and the smaller values of $\zeta^{K_{J}^{(*)}}_{\perp,\parallel}$ . Furthermore, if the spin of $K_{J}^{(*)}$ becomes larger, the branching fractions will be further suppressed due to the smaller Clebsch–Gordan coefficients defined by the polarization tensors of the $K_{J}^{(*)}$ . We also calculate the forward–backward asymmetry of the $B\to K_{J}^{(*)}\ell^{+}\ell^{-}$ decay, for which the zero is highly insensitive to the K-resonances in the LEET parametrization.     

Fe-doped SnO 2 nanopowders obtained by sol–gel and mechanochemical alloying with and without thermal treatment

The present work is aimed to compare the physical properties of $\mbox{Sn}_{1-x} \mbox{Fe}_x \mbox{O}_{2-\delta } $ (x?=?0, and 0.05) nanopowders obtained by sol–gel method, mechanochemical alloying, and mechanochemical alloying followed by thermal treatment. The X-ray diffraction of $\mbox{Sn}_{1-x} \mbox{Fe}_x \mbox{O}_{2-\delta } $ samples prepared by sol–gel showed peaks due to the cassiterite phase of SnO₂ and thier Mössbauer spectra showed ferromagnetic and paramagnetic signals. The samples obtained by the milling process of SnO₂ mixed with $\upalpha $ -Fe showed Bragg peaks due to SnO₂ (rutile) with a line broadening caused by the reduction of grain sizes and the presence of microstrains. Mössbauer spectra for these samples revealed the presence of Fe^3?+? as well as unreacted $\upalpha $ -Fe. In the case of mechanochemical alloying with thermal treatment, the incorporation of Fe^3?+? in the SnO₂ structure with the presence of impurities was observed.     

Study of Light Hypernuclei by the (e,e′K +) Reaction

We have been performing Λ hypernuclear spectroscopic experiments by the (e,e′K ⁺) reaction since 2000 at Thomas Jefferson National Accelerator Facility (JLab). The (e,e′K ⁺) experiment can achieve a few 100 keV (FWHM) energy resolution compared to a few MeV (FWHM) by the (K ^?, π ^?) and (π ⁺, K ⁺) experiments. Therefore, more precise Λ hypernuclear structures can be investigated by the (e,e′K ⁺) experiment. ${^{7}_{\Lambda}{\rm He}}$ , ${^{9}_{\Lambda}{\rm Li}}$ , ${^{10}_{\Lambda}{\rm Be}}$ , ${^{12}_{\Lambda}{\rm B}}$ , ${^{28}_{\Lambda}{\rm Al}}$ , and ${^{52}_{\Lambda}{\rm V}}$ were measured in the experiment at JLab Hall-C. In addition, ${^{9}_{\Lambda}{\rm Li}}$ , ${^{12}_{\Lambda}{\rm B}}$ , and ${^{16}_{\Lambda}{\rm N}}$ were measured in the experiment at JLab Hall-A.     

Jeans instability in superfluids

Recent numerical studies of the coupled Einstein–Klein–Gordon system in a cavity have provided compelling evidence that confined scalar fields generically collapse to form black holes. Motivated by this intriguing discovery, we here use analytical tools in order to study the characteristic resonance spectra of the confined fields. These discrete resonant frequencies are expected to dominate the late-time dynamics of the coupled black-hole-field-cage system. We consider caged Reissner–Nordström black holes whose confining mirrors are placed in the near-horizon region \(x_{\text {m}}\equiv (r_{\text {m}}-r_+)/r_+\ll \tau \equiv (r_+-r_-)/r_+\) (here \(r_{\text {m}}\) is the radius of the confining mirror and \(r_{\pm }\) are the radii of the black-hole horizons). We obtain a simple analytical expression for the fundamental quasinormal resonances of the coupled black-hole-field-cage system: \(\omega _n=-i2\pi T_{\text {BH}} \cdot n\left[ 1+O(x^n_{\text {m}}/\tau ^n)\right] \) , where \(T_{\text {BH}}\) is the temperature of the caged black hole and \(n=1,2,3,...\) is the resonance parameter.